fallback method to call when micropip can't find a package.

[samuelcolvin]

It would be nice if there was a fallback method to provide a URL while micropip is unable to find a pure Python wheel.

Currently (while waiting for pyodide/pyodide#5388 to be released), I'm having to do

from packaging.tags import parse_tag  # noqa
from packaging.version import Version  # noqa

import micropip  # noqa
from micropip import transaction  # noqa
from micropip.wheelinfo import WheelInfo  # noqa
real_find_wheel = transaction.find_wheel


def custom_find_wheel(metadata: Any, req: Any) -> Any:
    if metadata.name == 'jiter':
        known_version = Version('0.8.2')
        if known_version in metadata.releases:
            tag = 'cp312-cp312-emscripten_3_1_58_wasm32'
            filename = f'{metadata.name}-{known_version}-{tag}.whl'
            url = f'https://files.pydantic.run/{filename}'
            return WheelInfo(
                name=metadata.name,
                version=known_version,
                filename=filename,
                build=(),
                tags=frozenset({parse_tag(tag)}),
                url=url,
                parsed_url=urlparse(url),
            )
    return real_find_wheel(metadata, req)


transaction.find_wheel = custom_find_wheel

Which seems excessively ugly.

I know I could use an index_url, but then:

1. I think it would stop micropip consulting the pyodide lock file first
2. would require more infra than I want to setup

[hoodmane]

What about using add_mock_package()?

[andycloke]

@samuelcolvin thank you for this workaround! It means I can support OpenAI until the next version of Pydodide is released.

FYI, your example is missing this: from urllib.parse import urlparse.